Abbott had “caused alarm late on Monday by innocently wandering into the gents in the Commons”, the Mail on Sunday said.

“After a man standing at the urinals pointed out her mistake, she said: ‘Sorry’ – before calmly heading to one of the cubicles and closing the door.”

According to the MoS, which reported on Abbott’s complaint against it in a piece by deputy political editor Glen Owen yesterday, Abbott claimed the story was “fabricated and malicious” and designed to provoke abuse.

The newspaper said it received a formal complaint last month, in which a representative of Abbott had copied in the Independent Press Standards Organisation, claiming the story had breached Clause 1 (accuracy) of the Editors’ Code of Practice.

IPSO confirmed it had been copied into correspondence relating to a complaint by Abbott’s office to the Mail on Sunday, but told Press Gazette it did not receive any formal complaint and so has taken no action.

Abbott could still ask IPSO to launch an investigation by issuing a formal complaint with the press regulator, however. Press Gazette has yet to receive a response to a request for comment from Abbott’s spokesperson.

The MoS said Abbott’s complaint included that the story was not supported by any evidence, that “the entire basis of [the] article is fabricated”, and that it had been published with the “sole aim of ridiculing” her.

The newspaper said the complaint has been ended after it told Abbott it had an on-the-record witness account from the man who had been in the toilets at the time and who was “outraged” by her denial of the story.

The anonymous witness told the paper that at about 10pm on 11 June Abbott “stumbled into the gents toilets”. He added: “She acknowledged me at the urinals and then went into one of the cubicles.”

After following its internal complaint investigation procedure, the MoS said it had informed Abbott on 29 June that it stood by the story and that it has not heard from the politician or her office since.